


Welcome to Serenity

by eatyourhartout



Category: Buffy the Vampire Slayer (TV), Firefly, Serenity (2005)
Genre: BAMF Buffy Summers, Canon-Typical Violence, Crossover, First Meetings, One Shot, Post-Episode: s07e22 Chosen, Reavers (Firefly)
Language: English
Status: Completed
Published: 2020-06-27
Updated: 2020-06-27
Packaged: 2021-03-03 20:27:32
Rating: Not Rated
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,731
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24941557
Author URL: https://archiveofourown.org/users/eatyourhartout/pseuds/eatyourhartout
Summary: It doesn't have to be Tuesday, her birthday, or a poorly thought out wish for Buffy's day to go completely sideways.Giles with a prophecy, a lame apocalypse and a dimension hopping demon, however, is more than enough to ruin Buffy's week.Or how Buffy sorta meets the crew of Serenity after saving their lives.
Comments: 5
Kudos: 37





	Welcome to Serenity

**Author's Note:**

> I've been reading these and there are not enough Buffy/Firefly crossovers, and I got kinda inspired to write one of my own. 
> 
> I don't own anything but my own words - BtVS and Firefly/Serenity universes are both to Joss Whedon's creative brilliance. 
> 
> The mandarin I use in this fic is from google translate or from the firefly/serenity wiki dictionary page. Mandarin chinese is not one of the languages I speak, so I apologize in advance if some of it is incorrect.

Buffy ripped the scythe out of a khaki demon’s neck, panting. Blue slime exploded everywhere, drenching her clothes in more of the goop. Buffy only just managed to leap out of the line of fire, the worst of it missing her completely. Blood dripped into her eye from a cut somewhere on her forehead. She glanced over her shoulder at Faith, her sister slayer whooping with glee as she cut down another on the massive blue demons. 

This year's apocalypse came with a side order of Aladdin’s Genie style demons that exploded when they died. _ Gross.  _

“Buffy! You gotta kill the big one!” Dawn shouted across the warehouse. Buffy had rolled her eyes when Willow’s coven’s transportation portal had dropped them in the packing district of this year’s apocalypse central hellmouth. What was with the big bads and abandoned warehouses? Would it kill them to once in a while have a fight for the existence of the world somewhere nice? Like the beach? Or a nice open field where Willow could make with the mojo and take out all the baddies? 

Buffy nodded back to her sister, and dove back into the fight, making her way to the giant blue demon standing on a catwalk over the battle, large teeth grinning out at them as he flashed in and out of sight, appearing and disappearing from the fight, trying to take out slayers one at a time. So far only Caridad was out for the count, and was currently propped up in the corner as Rona and Satsu defend the injured slayer. 

Taking a running leap, she catches the edge of the catwalk, and gracefully swings herself up and over. The blue demon turned around and a creepy smile spread across it’s ugly face. Buffy heaved out a sigh, the scythe swinging lazily down by her side. She knows what was coming next. 

“Slayer.” It growled. Buffy snorted. 

“Slayee.” She countered. It was almost sad. Even apocalypses were kinda boring nowadays. She sees demon, she slays demon. Watchers find new mini slayers, Buffy trains the mini slayer. Giles reads ancient prophecy about blue demons and portals and blue hands and a new not-vampy-sorta-undead-but-not-really (Giles called his translation of the prophecy rough. Buffy didn't disagree.) type evil on the rise, Buffy takes the slayer army and stops the apocalypse. Kinda like see sun, wear sunglasses. 

Funny, back in high school she would have loved for something like this to happen. For there to be other slayers protecting the world so she could finally retire. Now, Buffy almost wants to make a w-i-s-h for something interesting to happen. Not that she ever would. In her world, interesting usually lead to dead bodies or missing eyes or other associated badness. 

“You’re going to die today slayer.” It growled. Buffy shrugged. No she wasn't. But the demon doesn't know that yet. 

“Maybe fourth times the charm.” 

* * *

“Reavers!” Wash’s voice echoed through the transmitter just a moment too late. Mal resisted the urge to swear in every language in five systems. Then as the shadow of the Reaver ship fell over the field they were hiding in, he gave into that urge. Neither Zoe nor Jayne blinked at his language as they stayed frozen in the brush. 

“Wash, could use a pick up right about now.” His pilot snorted, but Mal could hear the beautiful sound of Serenity’s engines firing up in the background of the transmission. 

“Just get clear of the Reavers. M’ on my way.” Mal drew his gun. Zoe and Jayne were both already clutching their own weapons. 

“So I’m fixin to get outta here. Thoughts?” But before either of them could reply blue light crackled through the air, filling the clearing right in front of the loading bay of the Reaver ship. A tiny slip of a girl came flying through the light, slamming into a tree, collapsing to the ground, clutching a shiny silver and red axe. She looked up, flipping her hair over her shoulder as a massive, blue, fanged  _ something _ followed, a manic grin spread across it’s ugly mug.

“What in the hells is that wei shian dohn woo?” Mal shrugged, hand teasing over the trigger of his gun as he watched the fight. The girl and the guàiwù exchanged furious blows, and blue light continually flared across the clearing, the two fighting figures vanished and reappeared each time the light appeared. 

“Wash where are you?” Mal hissed into the radio. He wasn’t unaware that the goram Reavers hadn’t exited their ship in a flood of death and near unstoppable destruction, but that didn’t mean that they wouldn't still come out to play. He’d very much like to be off world and breaking atmo by the time they decided to do so. 

Blue light flashed again, and Mal’s attention snapped back to the fight taking place in the clearing. Zoe’s hand was gripping his forearm somethin fierce, and he wouldn’t be surprised to find finger shaped bruises imprinted onto his skin a little later. Neither his lieu or his merc had moved, just as fascinated as Mal by the insane fight raging in the clearing. Something that small, and blonde, and well, pretty, shouldn’t be capable of such large levels of breathtaking violence. Except for River that one time in Mingo and Fanty’s bar. And even then, this girl was clearly out of even River's brainwashed assassin brained league. But where did this girl learn to fight like that? River was Alliance trained and brainwashed. The girl hasn't busted out fighting like that since. This girl knows exactly what she's doing - no brainwashing here. No way is this girl Alliance trained. 

The blonde kicked off a tree, flipping through the air over the blue monster, kicking it in the head as she went. Landing on the ground, she pushed off swinging that axe of hers as she went, scoring a deep gash along the blue thing’s arm. The girl let out a shout as the blue thing backhanded her, sending her flying, but she reoriented herself, never losing grip of her weapon. She kicked out and the blows were fast and vicious - Mal could hardly track the fight when the girl ducked a punch and slashed forward with her massive shiny red axe lookin thing and sliced something off the blue thing’s arm. 

“Ha! No more teleporting!” She cheered, as she swung the axe again. The blue thing ducked and stumbled back into the Reaver ship. Mal’s eyes widened. So far the Reavers hadn’t come out yet, which in his book counted as a God given miracle considering his luck.  But now that the blue thing had gone knocking...

The loading ramp lowered with a strained hiss, the broken down ship screeching in protest as Reavers stormed out of the ramp and leapt into the fight. 

“That girl is humped.” Zoe whispered. Mal groaned, glancing at his two crewmates. The three of  _ them _ were goram humped for not getting the hell out of there while they had the chance. Now, if they were lucky - they’d get a chance to fight their way out. If not… well, hopefully he won’t have to find out. 

The girl whipped around to the note the swarming Reavers, and if Mal wasn’t mistaken, rolled her eyes. 

“Today just isn’t my day is it.” She muttered, vaguely irritated, turning away from the  _ gorammed Reavers _ , and returning to her fight with the big blue thing. Before he could even try to puzzle out what the gorram hell  _ that _ meant - girl is fightin a bonafide alien monster creature while about to get swarmed by Reavers, he’d like to know what qualified as a  _ bad _ day for her - the radio at his side crackled to life. 

“Almost there cap’n. Get ready, cause we’re coming in hot.” Mal didn’t bother checking if Zoe and Jayne heard. He knew they had, and even if they hadn’t they follow his lead - even if Jayne would grumble and complain about it the entire time. The three of them shifted their weight, getting to slightly numb feet, prepared to make a break for Serenity as soon as she arrived. 

The girl smashed her axe into the side of the blue thing’s head and it collapsed to the ground. Twisting her body, the girl kept the momentum of the axe going as she sliced into the first wave of Reavers. 

“That girl is just as ruttin’ moon brained as the doc’s mei mei.” Jayne muttered. Mal risked a glance at the merc’s face to see the sheer awe plastered across his face. The man looked about ready to get down on one knee and propose. Mal looked back and didn’t blame the man. The girl was poetry in motion. She made River’s bar fight look like the kind of down and dirty brawl he likes to get into every U Day. He has no doubt that the girl in front of them would kick River's ass as easily as River had kicked Jayne's. 

Air rushed over them, and the sweet hum of his Serenity’s engines washed over him. Reavers screamed as they looked up at the sky towards the shining hull of his ship. A grin crossed Mal’s face, and without a word the three of them popped up and made a break towards the ship, shooting wildly over their shoulders at the Reavers that broke away from the girl to follow them. He glanced back over his shoulder at the girl. Thanks to the distraction, the girl was swirling through the Reavers, bodies dropping like flies. As long as that girl wasn’t overwhelmed she’d be fine. He pushed away the twinge in his half dead, mostly mangled conscience as he noted the second wave of Reavers exiting the other ship. 

It didn’t sit quite right with him, leavin that girl behind to die. But if he stuck around, he’d get his crew killed. And at the end of the day, crew was more important than a badass blonde girl. He reached the end of the Serenity ramp and leapt on board. Zoe and Jayne were already firing into the crowd of Reavers. He twisted around and started shooting, calmly firing into the crowd, dropping a Reaver with every bullet fired. River screams behind them, jabbering out an incomprehensible mess of words and phrases, fragmented into chains of incoherent thought. 

The girl in the clearing looks up, and her eyes widen as she takes in the Reavers chasing after them. She swings the axe like a bat, clearing some space around herself. The girl makes a running jump and flips over the heads of the Reavers and plants herself in between the ship and the approaching cannibals. 

“Well none of you are going to be winning any beauty contests anytime soon.” She commented glibly before lunging forward and attacking. 

“Get out of here!” The girl shouted over her shoulder, ducking under the wild swing of a Reaver and slicing her shiny axe through its head. She kicked another one and in the same movement managed to decapitate another two and cut off the arm of a third. 

Goramit. Now they _can’t_ leave her behind. Not if she’s protecting crew. Sometimes Mal wishes that his Ma hadn’t instilled quite so many values into him as a kid. 

“Cap’n we’re ready to go.” Wash’s voice echoed over the ship’s speakers. Zoe took one look at him and groaned. She shot off several more rounds before dashing to the intercom. 

“Keep us ready to go. The captain’s fixn to do something stupid, make himself into some kind of hero.” Mal leapt off the ship, firing as he marched towards where the girl whirled through the Reavers. Most of the gorammed things were dead, but still plenty left to kill them all if they boarded Serenity. The girl barely glances back towards him as she hacks and slashes at the Reavers, cutting them down like they were nothing. More bullets flew around him, and he knew Jayne at least had followed behind him, judging by the angry roars behind him as the big merc fired Vera in one hand, and slashed with his massive hunting knife with the other.

“MAL LOOK OUT!” Kaylee’s voice rang out and he glanced up in time to see the big blue guàiwù from before, pull back a fist, a long pointed skewer, shinning white, coated in a clear, blue tinted substance, shooting out from it’s wrist, and try to gut him with a punch. He dropped down, rolling away from the monster, before firing the rest of his clip at the thing. It didn’t even flinch, and just kept coming. Mal dodged back, trying to avoid tripping over Reaver bodies as the blue thing continued to try and kill him. 

“A friend of the Slayer?” It asked, staking after him. The blue thing was faster than that, Mal had seen it move while fighting the girl. But for right now it seemed content to just toy with him. 

“Friend of the who now?” He asked, stalling as he reloaded his gun. The blue thing didn’t answer the question - it just licked it’s chops and smiled, exposing an uncomfortable number of sharp lookin teeth. Mal’s back hit a tree. 

“You will die now.” Mal raised his gun. If eight rounds hadn’t even slowed it down, he doubts another twelve or twenty or forty would do much good either. But no way was he going down without a fight. 

“Hey! Papa Smurf! Come pick on someone your own size.” Mal’s head snapped towards the voice of the blonde - possibly named Slayer, which is a weird name for anyone, let alone a tiny slip of a girl like that. She had a fist propped on her hip, her head tipped to the side all cocky like. It's funny, cause no matter how tiny was was, no way could anyone mistake that girl for anything but the fighter she is. The prey part of his brain was cowering at the sight of a predator, while the rest of him was frozen in shock that the little blonde girl - or woman, because no way was that girl much younger than Simon. 

Blood dripped down the side of her face from a cut on her forehead, the rust red liquid half dried on her cheek. The red axe was held easily in her hand. 

“Very well. You will die first Slayer.” It growled. The girl flipped her hair. 

“No I won’t.” Mal liked the attitude. But the girl was gorammed tiny, and she’d already fought this thing once, then fought her way through a pack of Reavers. No matter what Kaylee may think, a positive cheerful like attitude can't fix everything. He carefully lifted his gun again. Maybe he could distract the thing while she killed it. But before he could even tickle the trigger, the two had launched back into a blur of motion, making it impossible for him to take a shot without risking blowing the girl’s head off instead of the blue thing’s. 

Mal saw a flash of shining white, and the world slowed. In his head he knew that it was really only a couple of seconds. But his eyes saw it go down in the span of what felt like minutes. The girl’s eyes flicked up to the sharp pointy skewer coming out the things arm. She hefted the axe, and kicked off the ground, using the thing’s punch as momentum to launch her higher. The skewer stabbed into her side, and she let out a huff of pain, her arm swinging back, sunlight glinting off the red blade, dripping with Reaver blood. 

She gripped the thing’s arm tighter, the blue monster looking vaguely surprised for having actually landed the blow, and  _ pulled _ . Mal would swear to Zoe later that he heard the soft squish of her body as she forced the blue thing’s arm weapon skewer  _ deeper into her own body _ . Her axe cut through the air with a soft whistle and the blade neatly sliced through its neck, the girl kicking off it’s chest to catapult herself away from the monster that was  _ suddenly exploding into goo. _

The girl flipped gracefully, and landed neatly on her feet. For a moment, the world was frozen, and it looked like everything was going to be fine. 

Then the girl - maybe named Slayer, which Mal still found to be a name of the highest ridiculousness - collapsed to the ground. The axe clattered to the dirt next to her, her hand still loosely gripping it. If he’d been a little less worried about his crew’s savior bleeding out in front of him, he’d probably be impressed. It’s hard to hold onto your weapon in a fight like they just had - let alone when you’re injured and in the business of keelin over from the holes in your body. 

“SIMON!” Mal bellowed, falling to his knees next to the girl. Golden blonde hair spilled across the ground, blood seeping over the earth. He quickly pressed his hands over the gaping wound in her stomach, blood pumping up and spilling through his fingers to the unsteady beating of her heart. Bruises littered her skin, along with dozens of minor scrapes and cuts. Faint scars criss crossed her skin, a line of puckered skin twisting along her shoulder, faint white lines slashed across her hands. A set of jagged - were those  _ teeth?  _ \- marks marched across the side of her throat, where someone had clearly tried to tear her throat out. Callouses from carrying and using weapons lined her hands, and dark scars scattered across her knuckles, evidence of a countless battles fought with her hands. Girl was a brawler. 

This girl lived a fighting life, clear as day. He would have known it even if he hadn’t seen her fight that blue thing, if he hadn’t seen her tear through a pack of Reavers like a well trained, well oiled killing machine, to protect his ship and his crew. If he hadn’t watched her intentionally take an impalement through the gut to kill the blue thing while protecting  _ him _ like he was some kind of damsel in distress. 

Mal would bet his Serenity that the girl was a soldier. And considering that she hadn’t even blinked at his uniform standard brown coat, she’d probably fought with the Independents. 

“Hey, hey. Wake up girl. Don’t go dyin' on us yet.” He tapped the side of her face, trying to wake her up. Zoe crashed to her knees beside him, bellowing over her shoulder for Simon. Hazel eyes fluttered open, and widened as she caught his gaze. 

“Come to kill me again Caleb? Make it stick this time? No… you can’t kill me. I already killed you.” A delirious laugh bubbled out of her throat, blood trickling out of her mouth as the laughter turned into a harsh cough. Mal exchanged a confused look with Zoe. Who the gorram hell is Caleb? Simon skidded to a stop next to them, his bag already open, supplies tumbling out as he rapidly checked her pulse and began to try and staunch the bleeding. He tore open the half shredded shirt, and dug out a roll of gauze without even glancing into his bag. 

“From beneath her it devoured. Bad evil preacher man had to split. One half left, one half right. Cut straight down the middle with the blessed Slayer Scythe. Mal is our captain and the only preacher here is our Shepherd.” River hovered in the doorway, brown curls tumbling in a curtain over half her face. Kaylee grabbed onto the teenager, holding her back as Simon worked to try and stabilize the bleeding girl. Mal suppressed the urge to groan. He did not have time to deal with River’s crazy and creepifying words today. They just barely survived Reavers, and some strange girl appears out of nowhere and saves their collective asses. 

The girl’s eyes widened with every word River spoke, and she jerked on the ground, trying to sit up. A strangled groan slipped through her lips as the abortive movement jostled the gaping hole in her side. Mal and Zoe both lunged, struggling to hold her still as Simon shouted in alarm. Her face went white as she stared at River. 

“How did y-” Her voice died and she slumped back to the ground. Mal caught her head before she dropped. Simon lifted a hypo of what probably had contained a sedative, and possibly also painkillers, away from the girl's neck, and heaved out a heavy sigh before sitting up. 

“I need to get her into the infirmary. This is deep, but it’s clean. I don’t think she’ll die.” Simon carefully repacked his medbag, his sleeves rolled back, bright red blood smeared across his arms. Mal nodded and he and Zoe carefully lifted her up, keeping her as level as possible. 

“In every generation there is a girl. One falls and another rises. The Chosen one, then two, then hundreds of sisters. Now only she is left. Two by two the men of blue wanted to make another. They couldn’t. Not Chosen. I wasn’t Chosen. Only filled with limitless Potential until they cut me open and pulled me inside out and forgot to put me back together again. They stole Potential away from me. Now she will kill them all. And nothing in the ‘verse will stop her.” A dreamy smile split across River’s face. A shiver went down Mal’s spine. He has nothing against anyone who wanted to pick a fight with the ruttin Alliance - ‘specially if they was gonna get River some kind of revenge for what they did to her at the ruttin Academy.

But something about the violence the girl just casually committed, and the warning in River’s voice made him worry. If this girl - if Slayer - was what they wanted River to turn into, what the hell was this girl going to be like when she was all awake again? 

River drifted forward, bare feet delicately gliding over the ground, like she was dancing as she skipped around the blood pooled across the floor. She easily shook off Kaylee’s restraining hand, approaching the unconscious blonde. River gently pressed her palm to the blonde’s cheek, cupping her face. Leaning down, she pressed a soft kiss to her cheek. 

“Hello jie jie. Welcome to Serenity.” 

  
  
  


**Author's Note:**

> Translations in order of appearance: 
> 
> wei shian dohn woo - dangerous animal/person
> 
> guàiwù - monster
> 
> mei mei - little sister
> 
> jie jie - big sister


End file.
